1. Field of the Invention
The present invention relates to a kick down shift control apparatus of an automatic transmission and more particularly to a kick down shift control apparatus of an automatic transmission which reduces its transmission oil pressure at the time of a kick down shift if the output of an engine is low.
2. Description of the Invention
In general, an automatic transmission applied to an auto vehicle adjusts oil pressure by enabling a shift control apparatus to control a plurality of solenoid valves according to a running speed of a vehicle, the open rate of a throttle valve and other sensed conditions, so that the transmission gear of a target transmission stage is operated for an automatic transmission.
In other words, in the case of the automatic transmission that automatically performs shifts, as described above, if a driver shifts a selection lever to his or her desired range, a manual valve changes to its port and controls the pressure of oil supplied from an oil pump to selectively operate a plurality of operational factors of the transmission gear mechanism according to the duty control of the solenoid valves for accomplishment of shifts. The automatic shift control apparatus determines a shifting stage by a preset program of a memory classified according to the open rate of the throttle valve and a speed of a car and, then, outputs a duty control signal related to the determined shifting stage to the solenoid valve, thus completing a shift.
The automatic transmission that operates according to the aforementioned operational principles may have friction factors in the course of shifting to a target shift stage when it starts or stops its operation. The shifting quality of the automatic transmission is determined depending upon the timings when the friction factors may start or stop their operations.
However, since the conventional automatic transmission performs the kick down shift at the same transmission oil pressure regardless of changes in the output of an engine, there has been a problem of causing a shifting shock to the automatic transmission because there occurs a delay in increasing the number of engine rotations if the kick down shift is carried out while the output of the engine is kept low due to a rising of an intake air temperature or an operation of a car air conditioner.
It is an object of the present invention to solve the aforementioned problems and provide a kick down shift control apparatus of an automatic transmission and a method therefor, the apparatus which reduces its transmission oil pressure and relieve a shifting shock at the time of a kick down shift while the output of an engine is low due to a rising of an intake air temperature or an operation of a car air conditioner.
In order to accomplish the aforementioned object of the present invention, there is provided a kick down shift control apparatus of an automatic transmission of a vehicle, the apparatus comprising:
vehicle running state sensing means for checking a running state of the vehicle;
engine control means for controlling engine outputs in response to a signal sensed by the vehicle running state sensing means and outputting information on the temperature of intake air and the operational state of an air conditioner;
shift control means for outputting a control signal to correct the pressure of transmission oil according to the temperature of intake air and the operational state of the air conditioner input from the engine control means, if conditions for a kick down shift are met with reception of the signal checked by the vehicle running state sensing means; and
driving means for controlling the oil pressure discharged out by the oil pump according to the control signal output from the shift control means and performing a shift by providing the oil pressure for a relevant fiction factor.
In addition, there is also provided a method for controlling a kick down shift of an automatic transmission, the method comprising the steps of:
discriminating whether conditions for a kick down shift are satisfied while a vehicle is in motion;
discriminating whether the temperature of intake air is higher than a reference temperature if all the conditions are satisfied for the kick down shift; and
adjusting a transmission oil pressure if the temperature of intake air is higher than the reference temperature, and performing the kick down shift with the adjusted transmission oil pressure.
Also, there may be additional steps of discriminating whether an air conditioner is in operation, adjusting the transmission oil pressure if the air conditioner is in operation, and performing the kick down shift with the adjusted shift oil pressure.